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Abstract: In this paper, there are represented the features of acousto-optic interaction in the context of pulse signal detection. It specifies the necessity of the development of a simpler method for the calculation of a demodulator output signal parameters in case of its feeding with a pulse signal. Approximation models of modulating pulse and a pulse of the photodetector’s output were made based on geometric representation of the photo-elastic interaction. It is shown the main parameter defining the shape of the output pulse is the inertia of the acousto-optic demodulator. It is postulated that this parameter is shaped due to the influence of two factors: an acoustic-optic interaction and a photodetector inertia. For estimation of the degree of influence of these factors, a numerical analysis based on developed models is carried out. The results of theoretic research and numerical analysis are verified with experimental research. It is stated that for the application of a high-performance photodetector, the inertia of the acousto-optic demodulator is defined mainly by space-time parameters of acousto-optic interaction. PubDate: 2023-08-01
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Abstract: N-order bandpass filter (BPF) with parallel resonators and cross and mixed couplings can have (N + 1) transmission zeros (TZ) located on the complex plane s = σ + jω. TZs at real frequencies (jω axis) are also called attenuation poles (AP). The authors propose an alternative possibility of AP forming in filters using resonators with special properties, which significantly increases the AP number from (N + 1) to (3N + 1). Increasing the AP number with fewer resonators allows us to increase the selectivity and rejection level and reduce BPF insertion losses. The special properties of resonators are that their input admittance Y has one or two poles (ωp1, ωp2) located next to the resonance frequency ω0. This leads to the appearance of AP in a BPF. We propose and analyze three resonators with special properties. They are formed by a cascade connection of a quarter-wave resonator and lumped L and C. The input of the resonators is located on the side of the lumped elements. It was found that the Q-factors of lumped elements do not affect the filter losses in the passband. The reduction of QL and QC leads only to the decrease of the AP “depth.” For the first time, 7 APs were implemented in the experimental second-order microstrip BPF. PubDate: 2023-08-01
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Abstract: The paper investigates the influence of the surface morphology of an array of silicon nanowires (SNW) on their humidity-sensitive characteristics. In this work, diode-type moisture sensors based on silicon nanowires were synthesized. SNWs were synthesized by the method of metal-stimulated chemical etching, and a p–n junction was formed in the SNW array by diffusion. The surface morphology was studied by the method of atomic force microscopy. The electrical and moisture-sensitive characteristics of the humidity sensors were measured. The influence of the root mean square value (RMS) of surface roughness and the volume porosity of material on the performance of the devices was determined. In particular, it has been shown that an increase in the surface roughness of the silicon nanowire array leads to a significant increase in the response (by up to 72.5 times), as well as a decrease in the response time and the recovery time of humidity sensors amounting to 20 and 36 s, respectively. On the other hand, the reduction of the roughness RMS leads to an improvement in reversibility (up to 11.3%), short-term stability (up to 1.61%), and repeatability of the sensor signal (up to 0.45%). The importance of taking into account the relationship between the surface morphology of the array of nanowires and their humidity-sensitive characteristics for the development of high-performance nanowire-based sensors has been demonstrated. PubDate: 2023-08-01
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Abstract: Unlike the known modulation method, the formant-modulation method for the evaluation of speech intelligibility allows the evaluation of not only the speech transmission index but also the articulation index. This paper presents the results of a study of the accuracy of speech transmission index evaluation using the full and rapid variants of the formant-modulation method. The study is carried out by the computer simulation method for two cases, namely, the case of the predominant effect of noise interference and the combined effect of noise and reverberation in a room of medium volume. Dependences of the systematic and random components of the estimation error of speech transmission index on the duration of the test signal and signal-to-noise ratio are obtained. It is shown that although the fast version of the formant-modulation method is 4–5 times inferior to the full version in terms of measurement accuracy of the speech transmission index, the desired estimation accuracy can be achieved if the duration of the test signal is sufficiently long. In particular, the bias and standard deviation of the estimate of the speech transmission index obtained by the fast formant modulation method do not exceed 0.03 and 0.014, respectively, for the test signal duration of 16 s. PubDate: 2023-08-01
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Abstract: The performance of the Fisher-Snedecor (F) fading model with selection combining (SC) diversity scheme over the interference-limited system is presented in this paper. The probability density function (PDF) and cumulative distribution function (CDF) are derived without SC diversity under single-user interference. After that, the expressions of CDF and PDF for SC diversity are computed. The PDF is presented for different desired and interferer multipath fading parameters. The results are also illustrated in terms of outage probability (OP) for independent but not necessarily identically distributed (INID) and independent identically distributed (IID) variates. The higher number of diversity branches shows better OP performance. PubDate: 2023-08-01
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Abstract: In this paper a broadband transition from coaxial line to circular waveguide has been proposed, developed, and experimentally investigated. The transition consists of series-connected sections-transitions based on microstrip line, antipodal fin line with and without overlapping fins, bilateral fin line, and tapered transition from a rectangular waveguide to a circular one. Taking advantage of fin lines ensures manufacturability and repeatability of the electrical characteristics of the transition. Simulation results obtained are in good agreement with the results of the experimental study. The proposed transition from a coaxial line to a circular waveguide ensures a reflection coefficient of no more than –10 dB in the 8–18 GHz operating frequency range. PubDate: 2023-07-01
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Abstract: The paper considers a nonparametric method for estimating the Doppler frequency of a broadband signal with code (digital) phase manipulation distorted by multiplicative interference. The estimation of the Doppler frequency, which leads to the deformation of the envelope and shift of carrier frequency, was carried out in the absence of a priori information about the probability density function of the noise component in the model of the received signal (observation). An assumption is made that the noise component is an independent and identically distributed (IID) process with independent and identically distributed random quantities (“white” noise). The objective function (OF) is proposed that uses BDS statistics of discrepancies, i.e., the difference between an observation and the expected signal model, to estimate the Doppler frequency. The OF minimum is adopted as an estimate of the parameter. Quality characteristics of the Doppler frequency estimation are investigated in the case of additive noise when observing a signal with different probability distributions: Gaussian, uniform, logistic, and Cauchy. Special attention is paid to the case when the probability density function of multiplicative interference is characterized by “heavy tails.” The statistical modeling of the Doppler frequency estimation algorithm that implements the numerical minimization of the proposed objective function has been carried out. It is shown that the use of BDS statistics and the proposed objective function based on it allows us to avoid specifying the distribution density of the multiplicative interference when determining the Doppler frequency. PubDate: 2023-07-01
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Abstract: The ever-changing diversity of users and high-specification devices have become key concerns for the current mobile network operators. In this paper, a max-min fair dynamic power control algorithm is proposed for the reduction of power consumption at a base station. The spatial heterogeneity of users is achieved by applying a stochastic geometry-based Cox process. The set-up network is analyzed using the mmWave spectrum at deployed small cells (SCs) and with sub-6 GHz in macrocell (MC). The simulated MATLAB results depict an increase in the network sumrate and average user throughput when changing from the fixed power allocation to the proposed dynamic power allocation algorithm. PubDate: 2023-07-01
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Abstract: This paper examines the efficiency of a downlink non-orthogonal multiple access (NOMA) system by using a deep learning (DL)-based stacked long short-term memory (S-LSTM) scheme. The vehicle-to-vehicle (V2V) channel is considered to be time-selective as a result of node mobility and the presence of imprecise channel state information (CSI). The use of the fifth generation (5G) tapped delay line type C (TDL-C) independent and identically distributed (IID) fading channel models allows for the production of channel taps that properly replicate the Nakagami-m fading wireless channel. The paper examines the outage probability (OP) and symbol error rate (SER) of both traditional and suggested channel estimators. It analyzes these metrics under various fading parameters, pilot symbols (PS), learning rate (LR), and batch size. The training of deep neural network (DNN) models is performed using the Adam optimizer. Enhancing the signal-to-noise ratio (SNR) may decrease the SER which results in the enhanced identification of the downlink channel in NOMA cell-based systems. Reducing the LR has a positive effect on the SER, validating the analytical findings that indicate greater changes in DNN weights and larger validation mistakes when the LR is raised. Nevertheless, this benefit is accompanied by the drawback of more frequent updates, resulting in a delay in the model’s convergence. PubDate: 2023-07-01
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Abstract: This paper elucidates the importance of creating backup communication channels in emergencies when access to cellular and satellite communication systems can be limited. The purpose of the study is to substantiate the use of LoRaWAN technology as a basis for building reliable backup communication facilities. A block diagram of the device has been proposed, which is used as an example for modeling the autonomy time of the device. It is shown that, depending on the mode of operation, this time ranges from 150 to 900 days. To estimate the radio accessibility zone of the device, the maximum transmission range was modeled using various models of radio wave propagation. The results of the investigations have shown that the developed emergency communication system based on the LoRaWAN protocol is effective and superior to other wireless communication technologies under certain conditions. PubDate: 2023-06-01
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Abstract: Recently, due to the fast development in multimedia applications of wireless communication systems and demands of increasing the capacity and data rates to meet the requirements of 5G mobile communication systems, new transmission techniques are needed. One of the powerful enabling tools of the 5G communication systems is the multi-input multi-output (MIMO) antenna system employing multiple antennas and utilizing the multipath fading mobile environment to increase the channel capacity without any additional bandwidth and/or transmitted power. However, because of the limited space of mobile devices, the distances between antennas are decreasing. The mutual coupling between antennas severely affects the overall performance of the MIMO system. So, isolation improvement methods are applied to reduce these influences. In this review, different isolation techniques and their features and drawbacks are presented, and the techniques for applying them in modern MIMO antenna systems are illustrated. Besides, the performance characteristics of these MIMO systems are compared. The review also contains basic concepts of the MIMO antenna system and its performance metrics. Finally, the future directions and trends for the MIMO antenna system design are discussed briefly. PubDate: 2023-06-01
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Abstract: Against the background of the intensive development and implementation of satellite technologies for position determination, navigation, and time synchronization, one of the central threats to critical industries is the creation of intentional interference to the signals of global navigation satellite systems. It is shown that the use of small-sized antenna arrays in navigation systems consisting of satellite constellations of GPS, GLONASS, GALILEO, BEIDOU, QZSS, or their combinations makes it possible to detect and suppress interfering signals by forming zeros of the antenna array directional pattern in the directions of their arrival. The interfering signal suppression is supplemented with detection procedures while maintaining the ability of navigation by using from one to four satellite systems according to criteria of the required number of satellites in the line of sight and the permissible geometric factor. The process of suppressing the interfering signal from four directions is illustrated by three scenarios, the initial data for which are signals from 35 satellites in the line of sight collected in real-time from five systems. It has been shown that the use of five systems and 35 satellites ensures the suppression of the interfering signal. At the same time, 22 satellites are involved in solving the navigation problem, 13 satellites are below the detection threshold, and the geometric factor is 1.18. When using GPS, GLONASS, and 19 satellites, the interfering signal is suppressed. In this case, 10 satellites are involved in solving the navigation problem, 9 are below the detection threshold, and the geometric factor is 2.1. When using only GPS, the interfering signal suppression is also ensured. This time 7 satellites are involved in solving the navigation problem, 4 are below the detection threshold, and the geometric factor is 1.76. PubDate: 2023-06-01
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Abstract: This paper discusses N-order bandpass filter (BPF) with all mixed couplings between adjacent resonators, and between end resonators and loads. It has (2N + 1) transmission zeros (TZ) at real frequencies. To the existing (N + 1) TZs generated by mixed couplings, another N TZs are added, which generated by resonators with special properties. Each such resonator is a λ/4 resonator, in which the connection point is located relatively close to the short-circuited end. In this case, the input admittance of the resonator Y(jω) has a pole ωp, which is located to the right and at a small distance from the main resonant frequency ω0. This pole ωp of the Y(jω) function leads to the appearance of a right-handed TZ in a BPF characteristic. If we use N resonators with different connection points, then N additional TZs will appear. The design of that BPF is considered. The measured and simulated frequency responses of the second-order BPF with 5 TZs are presented. PubDate: 2023-06-01
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Abstract: This article highlights the potential advantages of the proposed hybrid algorithm for 6G. The algorithm’s adaptability addresses the dynamic spectral characteristics of 6G environments, enabling a seamless transition between different spectral conditions. The hybrid approach holds promise for enhancing spectrum utilization, reducing interference, and optimizing overall communication system performance. As 6G technology evolves, the integration of energy detection and cyclostationary spectrum sensing through the hybrid algorithm offers a glimpse into innovative techniques that can shape the future of wireless communication, unlocking the potential for enhanced connectivity, efficiency, and user experience. Several parameters such as the probability of detection (Pd), probability of false alarm (Pfa), bit error rate (BER), and power spectral density (PSD) are compared and analyzed with the conventional spectrum sensing algorithms. We see that the proposed hybrid algorithms obtain a substantial detection performance at the low signal-to-noise ratio (SNR). PubDate: 2023-05-01 DOI: 10.3103/S0735272723050023
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Abstract: The creation of smart healthcare systems is a viable strategy to improve the quality and availability of healthcare services. Identity theft, data breaches, and denial-of-service attacks are just some of the security concerns that have arisen as a result of connecting wireless networks and smart medical equipment. A secure and trustworthy smart healthcare system that can protect patient data and preserve the confidentiality of private medical information is especially important in light of these vulnerabilities. Medical diagnosis assumes increasing importance as the amount of data created daily in the 6G-enabled Internet-of-Medical Things (IoMT) grows exponentially. To enhance the anticipation accuracy and supply a real-time medicinal diagnosis, this research presents an approach integrated into the 6G-enabled IoMT that requires less human intervention for healthcare applications. To do this, the proposed system combines deep learning with optimization methods. MobileNetV3 architecture is then used to learn the features taken from each image. In addition, we improved the performance of the HGS-based arithmetic optimization algorithm (AOA). The operators of the HGS are used in the new approach, dubbed AOAHG, to improve the AOA operation capacity as the viable province is divided up. We design a 6G-enabled IoMT approach that requires fewer humans in healthcare settings but yields faster diagnostic results. The new approach was developed to be used in systems with limited means. The created AOAHG prioritizes the most important features and guarantees an overall upgrade in model categorization. When compared to other methodologies in the literature, the framework’s results were impressive. The created AOAHG also outperformed alternative FS methods in terms of the achieved accuracy, precision, recall, and F1-score. For instance, AOAHG had 92.12% accuracy with the ISIC dataset, 98.27% with the PH2 dataset, 95.24% with the WBC dataset, and 99.84% with the OCT dataset. PubDate: 2023-05-01 DOI: 10.3103/S0735272723060031
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Abstract: Industry 4.0 relies heavily on artificial intelligence (AI) and cloud computing (CC), both of which have been greatly aided by the 5-generation mobile network (5G). However, the arrival of 5G, is seen as a watershed moment that will radically alter the current global trends in wireless communication practices and the lives of the masses. 5G envisions a future where the digital and physical worlds merge. The 6th-generation (6G) wireless communication network will likely unite terrestrial, aerial, and maritime communications into a single, unified system that is both more stable and faster and can accommodate a far larger number of devices with ultra-low latency needs. The purpose of this research is to foresee a scenario in which 6G supersedes 5G as the dominant standard for wireless communication in the years to come. Several advances have been made, but the desired instantaneous global communication and computation with no latency has not arrived yet. In this paper, there are represented the most significant obstacles and difficulties that the transition from 5G to 6G can encounter on the way to realizing these loftier goals. The main purpose of “technology for humanity” is to improve service to the world’s most disadvantaged people, and this paper lays out a plan for 6G that includes the enabling technology infrastructures, obstacles, and research directions that will get us there. PubDate: 2023-05-01 DOI: 10.3103/S0735272723050047
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Abstract: The article proposes a new type of broadband patch antennas based on micro QR codes with integrated metamaterial cell as a marker. In this research, several design options were considered that used the variation of the metamaterial cell parameters. For their analysis, the numerical modeling methods of the Ansys EM Suite program were used due to the complexity of describing the interaction of antennas of non-Euclidean geometry with radio waves. Evaluation and comparison of proposed antennas was conducted by the following characteristics: amplitude-frequency response and voltage standing wave ratio. To expand the frequency band of the synthesized antenna has been implemented the split square marker is an element of micro QR. This approach enables the expansion of the relative bandwidth of the corresponding printed antenna to the value of 1.7267 under the condition of the continuous transmission band having a width of 167.935 GHz within the range from 13.29 to 181.225 GHz. In this case, cutouts of the split square marker are located along the line coaxial with the power supply line, and the cutout for the outer “ring” is located below. To synthesize micro QR code, the word “antenna” was used. PubDate: 2023-05-01 DOI: 10.3103/S073527272307004X
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Abstract: Current networks (such as 4G and the forthcoming 5G networks) may not be capable of fully congregating quickly emerging traffic strains due to the proliferation of smart fatal, infrastructures and the explosion of diverse applications with varying necessities. As a result, 6G network research has already seen participation from both the private sector and the academic community. Recently, an innovative paradigm has emerged for the intelligent design and optimization of 6G networks based on the combination of artificial intelligence (AI) and data science (DS). Therefore, this article proposes an AI-enabled architecture for 6G networks, which is alienated into four layers: intelligent sensing, data analytics, intelligent control, and smart application, to realize patterns sighting, smart resource management, automatic network adjustment, and intelligent service provisioning. We go over the uses of DS&AI methods in 6G networks, such as AI-enhanced mobile edge computing, intelligent mobility, and smart-spectrum management, and how to implement these methods to maximize the network’s performance. We also emphasize key areas for future study and clarifications for AI-enabled 6G networks, together with computational efficiency, algorithm resilience, hardware development, and energy management. PubDate: 2023-05-01 DOI: 10.3103/S0735272723050059
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Abstract: Future wireless communication systems can accommodate huge connections and improve spectrum efficiency by using the approach based on non-orthogonal multiple access (NOMA). High peak-to-average power ratio (PAPR) levels can, however, negatively affect NOMA, resulting in decreased system performance and more complicated power amplifiers. This study suggests PAPR reduction in NOMA by utilizing companding methods for 512, 256, and 64 sub-carriers to address this problem. The high peak power of NOMA signals may be effectively compressed by using nonlinear companding techniques, such as μ-law and A-law companding, which reduces distortion and improves overall system dependability. Simulations are used to assess the effectiveness of the suggested companding methods, and the findings show a significant reduction in PAPR assuring an increased bit error rate (BER) effectiveness and transmission resilience in NOMA-based communication systems. The suggested method is contrasted with the conventional A-law (C-A-Law) and μ-law (C-μ-law). PubDate: 2023-04-01 DOI: 10.3103/S0735272723040039
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Abstract: An experimental study of the effect of radiation emissions (neutrons, gamma radiation) on the sensitivity of industrial bipolar n-p-n magnetotransistors has been carried out. It has been shown that neutron irradiation leads to defects in the structure, which reduces the effective lifetime of the injected charge carriers and decreases the magnetosensitivity. Gamma radiation with increasing intensity first destroys the surface structural defects and increases the lifetime of carriers and magnetoresponsiveness, and then penetrates deeper forming defects and reducing magnetoresponsiveness. This makes it possible to use gamma radiation with an intensity of up to 107 R as a technological method of increasing magnetosensitivity. PubDate: 2023-04-01 DOI: 10.3103/S0735272723060055
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